This invention concerns impact tools useful in heavy work. It arises from the fact that conventional air or electric drive jackhammers such as used to break pavement are very expensive for situations where only a few blows are required. Also, as these tools require an air compressor or heavy electrical service, they have the serious disadvantage of extreme cumbersomeness. Sledgehammers and chisels are often not desirable substitutes because of being inaccurate and difficult to use. All of these tools are dangerous for the untrained.